U.S. Pat. No. 4,756,563 granted to Stephen K. Garwood and Jeffrey L. Konchan on Jul. 12, 1988 for a vehicle door latch, which is hereby incorporated in this patent specification by reference, discloses a known vehicle door latch comprising a plastic housing and a metal face plate that define a "fishmouth" slot that receives a jamb-mounted striker when the vehicle door is closed. The door latch also includes a fork bolt that is rotatably mounted in the housing on a pivot pin so as to swing in the housing between an unlatched position and a latched position where the fork bolt captures the striker in the fishmouth slot of the housing. A releasable detent holds the fork bolt in the latched position.
The housing includes an elastomeric bumper or cushion at the back or inboard end of the fishmouth slot that is engaged by the striker when the vehicle door is slammed shut to absorb energy and reduce noise during the door closure operation. The captured striker compresses the elastomeric bumper so that the striker biases the fork bolt against the detent.
U.S. Pat. No. 5,328,219 granted to Jeffrey L. Konchan, Alfred L. Portelli and Rita M. Paulik on Jul. 12, 1994 for a vehicle door latch shows another known vehicle door latch that also includes an elastomeric bumper or cushion at the back of the door latch slot to absorb energy and reduce noise during the door closure operation and to bias the fork bolt against the detent.
The composition of the elastomeric bumper and the amount of compression by the captured striker determine the stiffness of the vehicle door latch. Known vehicle door latches such as those discussed above have a relatively constant stiffness.
The stiffness of a vehicle door latch can affect vehicle ride quality directly along with vibrations in the steering column, floor pan and vehicle seats. Smaller cars are usually less concerned about these effects and more concerned about door closing and door opening efforts. On the other hand, larger cars are usually more concerned about ride quality which is affected by poor latch stiffness more easily than are smaller cars. Thus, the relatively constant stiffness of known vehicle door latches exemplified by the patents discussed above must be changed to tailor the vehicle door latch to each specific vehicle. The stiffness of known vehicle door latches such as those discussed above can be changed for each specific vehicle by using different elastomeric bumpers made of materials having different durometers. However, this solution proliferates the number of vehicle door latch designs, adds inventory and manufacturing costs and introduces the possibility of installing the wrong elastomeric bumper.